Semiconductor fabrication method and system

ABSTRACT

Embodiments of the present invention are generally directed to a method for manufacturing a semiconductor device. In one embodiment, the method includes providing a substrate that includes a via or interconnect. In this embodiment, the method also includes forming a sealed array, in which forming such an array includes attaching a carrier to a first surface of the substrate to form a sealed cavity between the carrier and the substrate. Further, the method of this embodiment also includes forming a redistribution layer on the sealed array over a second surface of the substrate. Devices and systems having a carrier attached to a substrate are also disclosed.

BACKGROUND

1. Field of the Invention

Embodiments of the present invention relate generally to the field ofsemiconductor devices. More particularly, embodiments of the presentinvention relate to the production of semiconductor devices, such asimage sensing devices, having a carrier disposed over a substrate toform a sealed cavity.

2. Description of the Related Art

Microprocessor-controlled circuits are used in a wide variety ofapplications. Such applications include personal computers, cellularphones, digital cameras, control systems, and a host of other consumerproducts. A personal computer, digital camera, or the like, generallyincludes various components, such as microprocessors, that handledifferent functions for the system. By combining these components,various consumer products and systems may be designed to meet specificneeds. Microprocessors are essentially generic devices that performspecific functions under the control of software programs. Thesesoftware programs are generally stored in one or more memory devicesthat are coupled to the microprocessor and/or other peripherals.

Electronic components such as microprocessors and memory devices ofteninclude numerous integrated circuits manufactured on a semiconductorsubstrate. The various structures or features of these integratedcircuits may be fabricated on a substrate through a variety ofmanufacturing processes known in the art, including layering, doping,and patterning. Obviously, the size of each feature directly impacts thenumber of features that may be formed on a substrate of a given size.Accordingly, it is generally desirable to reduce the size of suchfeatures in order to increase the number of elements that may be formedin a given area of the substrate.

In addition to microprocessors and/or memory devices, some systems, suchas digital cameras, generally include an image sensor (e.g., a chargecoupled device (CCD) sensor or a complementary metal oxide semiconductor(CMOS) sensor) configured to receive an image. Typically, such imagesensors include an array of sensor pixel cells or photoreceptors thatutilize the photoelectric effect to convert incident photons (i.e.,those photons striking the photoreceptors of the sensor) into electricalcharges. Once these photons are converted into electrical charges, amicroprocessor may process the electrical charges into digital data thatmay be stored and/or used to reconstruct the captured image.

SUMMARY

Certain aspects commensurate in scope with the originally claimedinvention are set forth below. It should be understood that theseaspects are presented merely to provide the reader with a brief summaryof certain forms the invention might take and that these aspects are notintended to limit the scope of the invention. Indeed, the invention mayencompass a variety of aspects that may not be set forth below.

Embodiments of the present invention generally relate to a technique forthe efficient fabrication of a semiconductor device, such as an imager,and to devices and systems including such semiconductor devices. In someembodiments, a carrier is coupled to a substrate to form a sealed cavitytherebetween. For example, the carrier may be adhered to the substratevia an epoxy or glue, or coupled in some other fashion. Additionally, incertain embodiments, the substrate may comprise an image sensorconfigured to receive light through the carrier and to convert the lightinto data.

Further, in some embodiments, a redistribution layer is formed on thesubstrate to facilitate electrical communication between components ofthe substrate and other external circuitry. The redistribution layer mayinclude some combination of passivation and conductive layers tofacilitate routing of electrical signals from the substrate components,such as an image sensor, to external circuitry. Also,under-bump-metallurgy features, such as plating layers and contactbumps, may be formed on or coupled to the redistribution layer tofurther facilitate such communication, and to permit efficient mountingof the substrate to some other component, such as a circuit board.

Still further, in some embodiments, the carrier is attached to thesubstrate and the redistribution layer is formed without using anyvacuum processes. For instance, in one embodiment, the carrier isadhered to the substrate in a processing environment having a pressurebetween 0.5 atm and 0.9 atm. In such an embodiment, the redistributionlayer may be advantageously formed through a variety of non-vacuumpressure processes, such as spinning-on passivation layers of theredistribution layer at or near atmospheric pressure, and forming aconductive layer through atmospheric pressure chemical vapor deposition.

Various refinements of the features noted above may exist in relation tovarious aspects of the present invention. Further features may also beincorporated in these various aspects as well. These refinements andadditional features may exist individually or in any combination. Forinstance, various features discussed below in relation to one or more ofthe illustrated embodiments may be incorporated into any of theabove-described aspects of the present invention alone or in anycombination. Again, the brief summary presented above is intended onlyto familiarize the reader with certain aspects and contexts of thepresent invention without limitation to the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a processor-based device inaccordance with one embodiment of the present invention;

FIG. 2 is a flow diagram of a method related to the manufacture of adevice in accordance with one embodiment of the present invention;

FIG. 3 is a cross-sectional view of a device having, among other things,a via disposed in a substrate and a carrier adhered to the substrate inaccordance with one embodiment of the present invention;

FIG. 4 is a cross-sectional view of a portion of the device of FIG. 3,depicting in greater detail the substrate and via of the device inaccordance with one embodiment of the present invention;

FIG. 5 is a cross-sectional view of the device of FIG. 4 following thethinning of the substrate in accordance with one embodiment of thepresent invention;

FIG. 6 is cross-sectional view of the device of FIG. 5, illustrating theaddition of a passivation layer to the substrate in accordance with oneembodiment of the present invention;

FIG. 7 is a cross-sectional view generally illustrating the addition ofone or more metal layers to the device of FIG. 6 in accordance with oneembodiment of the present invention;

FIG. 8 is a cross-sectional view depicting an additional passivationlayer formed on the device of FIG. 7 in accordance with one embodimentof the present invention; and

FIG. 9 is a partial cross-sectional view depicting the formation ofunder-bump-metallurgy (UBM) features on the device of FIG. 8 inaccordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Moreover, the use of “top,” “bottom,” “above,” “below,” and variationsof these terms is made for convenience, but does not require anyparticular orientation of the components.

Turning now to the drawings, FIG. 1 is a block diagram of an electronicsystem containing integrated circuit devices that may employ embodimentsof the present invention. The electronic device or system, which isgenerally referred to by the reference numeral 10, may be any of avariety of types such as a computer, digital camera, cellular phone,personal organizer, or the like. In a typical processor-based device, aprocessor 12, such as a microprocessor, controls the operation of systemfunctions and requests.

The system 10 may include a power supply 14, which may comprise abattery or batteries, an AC power adapter, or a DC power adapter, forinstance. Various other devices may be coupled to the processor 12depending on the functions that the system 10 performs. For example, aninput device 16 may be coupled to the processor 12 to receive input froma user. The input device 16 may comprise a user interface and mayinclude buttons, switches, a keyboard, a light pen, a mouse, adigitizer, a voice recognition system, or any of a number of other inputdevices. An audio or video display 18 may also be coupled to theprocessor 12 to provide information to the user. The display 18 mayinclude an LCD display, a CRT display, LEDs, or an audio display, forexample.

An RF sub-system/baseband processor 20 may be coupled to the processor12 to provide wireless communication capability. The RFsubsystem/baseband processor 20 may include an antenna that is coupledto an RF receiver and to an RF transmitter (not shown). Furthermore, acommunications port 22 may be adapted to provide a communicationinterface between the electronic system 10 and a peripheral device 24.The peripheral device 24 may include a docking station, expansion bay,or other external component.

The processor 12 may be coupled to various types of memory devices tofacilitate its operation. For example, the processor 12 may be connectedto memory 26, which may include volatile memory, non-volatile memory, orboth. The volatile memory of memory 26 may comprise a variety of memorytypes, such as static random access memory (“SRAM”), dynamic randomaccess memory (“DRAM”), first, second, or third generation Double DataRate memory (“DDR1”, “DDR2”, or “DDR3”, respectively), or the like. Thenon-volatile memory of the memory 26 may comprise various types ofmemory such as electrically programmable read only memory (“EPROM”) orflash memory, for example. Additionally, the non-volatile memory mayinclude a high-capacity memory such as a tape or disk drive memory.

The system 10 may also include an image sensor or imager 28 coupled tothe processor 12 to provide digital imaging functionality. The imager 28may include a charge coupled device (CCD) sensor or a complementarymetal oxide semiconductor (CMOS) sensor having an array ofphotoreceptors or pixel cells configured to be impacted by photons andto convert such impact into electrical current via the photoelectriceffect. While the imager 28 may be coupled remotely from the processor12, such as by way of a circuit board, the imager 28 and processor 12may instead be integrally formed, such as on a common substrate.

A method 30 for manufacturing a semiconductor device, such as theprocessor 12 and/or the imager 28, is generally provided in FIG. 2 inaccordance with one embodiment of the present invention. Particularly,the method 30 includes a number of steps 32-38, which are described ingreater detail below with respect to FIGS. 3-9. For instance, the method30 includes a step 32 of providing a substrate and a step 34 of forminga sealed array, as generally discussed herein with respect to FIGS. 3and 4. Further, the method 30 also includes a step 36 of forming aredistribution layer, as is generally discussed below in reference toFIGS. 5-8. Additionally, the method 30 includes a step 38 of forming oneor more under-bump-metallurgy features, such as a plating layer, contactbumps, or the like, as discussed with respect to FIG. 9. As will beappreciated, one or more of these steps may be performed in a reactor orprocessing chamber such that the environment in which the steps areperformed may be regulated.

Discussing first the steps 32 and 34, a sealed array or device 40, suchas a sealed imager array, is illustrated in FIGS. 3 and 4 in accordancewith one embodiment of the present invention. The device 40 includes asubstrate 42 having one or more through-wafer interconnects (TWI) orvias 44. For the sake of efficiency, the present technique may beimplemented as a wafer-level process, in which the substrate 42 is asemiconductor wafer having numerous die regions having various featuresformed thereon, such as an image sensor, thus facilitating simultaneousmass production of such devices 40. In other embodiments, however, thesubstrate 42 may be composed of other structures, such as an individualsemiconductor die, in accordance with the present technique.

In the presently illustrated embodiment, the vias 44 are formed in anupper surface 46 of the substrate 42, although similar vias could beformed instead on a lower surface 48 of the substrate 42 in otherembodiments. It should be noted that, in certain embodiments, the vias44 may be formed in the upper surface 46 prior to the attachment of acarrier 52 to the substrate, as discussed below, and/or the vias 44 maybe formed in the lower surface 48 before or after the attachment of thecarrier 52. Additionally, in an embodiment in which the substrate 42includes an image sensor, the substrate 42 may also include a layer 50of microlenses that serve to focus incoming light on the photoreceptorsof the image sensor, as depicted in FIG. 3.

The carrier 52 is coupled to the substrate 42 to form the sealed arrayor device 40. In some embodiments, such as that presently illustrated,the carrier 52 is generally positioned parallel to, and in spacedrelation with, the substrate 42 to form an interior region or sealedcavity between these two elements. In one embodiment, the carrier 52 isadhered to the upper surface 46 of the substrate 42 via an adhesive 54,such as an epoxy, glue, or the like. In various embodiments, the carrier52 may comprise one or more of glass, silicon, or some other suitablematerial that allows light to pass through the carrier 52 and impact animage sensor of the substrate 42 disposed within the sealed cavity, suchas the imager 28.

Additionally, in some embodiments, the carrier 52 is coupled to thesubstrate 42 at pressure rather than in a vacuum, such that the sealedcavity is pressurized. For instance, in one embodiment, the carrier 52is coupled to a substrate 42 within a processing chamber at a pressureless than or equal to 1 atm, such as between 0.5 and 0.9 atm. In such anembodiment, the pressure within the cavity will match that within theprocessing chamber when the device 40 is at a temperature identical tothat of the processing chamber during coupling of the carrier 52 to thesubstrate 42. Further, the pressure may be chosen such that the pressurewithin the cavity of device 40 reaches 1 atm at a desired temperature,such as 40° C., 45° C., or 50° C., for instance, to generally maintain apositive pressure differential between an exterior pressure and thepressure within the cavity and reduce the likelihood of damage to thesubstrate 42 or other components of the device 40 resulting from excesspressure within the cavity.

As illustrated in FIG. 4, a via 44 may include a dielectric material 56that at least partially isolates a conductive material 58 from otherportions of the substrate 42. The dielectric material 56 may be formedthrough a pulsed deposition layer process, or through any other suitableprocess. Further, in some embodiments, the conductive material 58comprises a metal, such as palladium, a copper-nickel alloy, or thelike. The conductive material 58 is disposed in contact with contactpads 60 to facilitate electrical communication between the conductivematerial 58 and other features of the substrate 42, such as an imagesensor. Additionally, in one embodiment, the remainder of the via 44comprises a fill material 62, such as polymer and/or solder.

Turning now to the step 36 of the method 30 (FIG. 2), the formation ofthe redistribution layer on the substrate 42 may be better understoodwith reference to FIGS. 5-8. Particularly, the lower surface 48 of thedevice 40 may be ground and/or polished such that the vias 44 areexposed along a lower surface 64 of the substrate 42, as generallyillustrated in FIG. 5. In one embodiment including a silicon substrate42, NH4OH is used to selectively etch the silicon to expose the vias 44.As may be appreciated, however, other materials and/or processes mayalso or instead be used to thin the substrate 42 and/or expose the vias44.

A passivation layer 66 may be added to the substrate 42, as generallyillustrated in FIG. 6. The passivation layer 66 includes a window 68that exposes an associated via 44. As will be appreciated, although notshown in the present, detailed view, the passivation layer 66 mayinclude a number of such windows 68 to expose a plurality of vias 44.The passivation layer 66 and the window 68 may be formed through anysuitable process. For instance, in one embodiment, the passivation layer66 is spun-on to the substrate 42 and patterned to form the window 68.Further, in one embodiment, patterning the window 68 may includeapplying a photoresist layer to the passivation layer 66, exposing anddeveloping the photoresist layer, etching the window 68 through theopening in the photoresist layer, stripping the photoresist layer, orthe like.

In one embodiment, a conductive layer 70 is then applied over thepassivation layer 66 and in contact with the via 44, as generallydepicted in FIG. 7. In the presently illustrated embodiment, theconductive layer 70 includes an aluminum sub-layer 72, which is disposedbetween a pair of titanium sub-layers 74. It should be noted that, inother embodiments, the conductive layer 70 may be composed of differentmaterials and/or a different number of layers or sub-layers other thanthose described immediately above, and may even be composed of a singlelayer of conductive material instead of a plurality of sub-layers. Forinstance, in other embodiments, the conductive layer 70 may comprise oneor more layers of copper, tantalum-nitride, or the like. Notably, insome embodiments, the conductive layer 70 is formed through anatmospheric pressure chemical vapor deposition (APCVD) process, asdiscussed in greater detail below.

Also, the conductive layer 70 may be patterned through various steps,such as resist and etch steps, to produce a desired configuration. Forinstance, in some embodiments, a photoresist layer may be disposed overthe conductive layer 70 and developed to expose certain portions of theconductive layer 70, which may then be removed via wet and/or dry etchprocesses. In one embodiment, the exposed portions of the conductivemetal layer 70 may be etched through a wet etch process that utilizesHNO₃, HF, and H₂O.

Following any desired patterning of the conductive layer 70, apassivation layer 76 may be generally disposed over a conductive layer70, as provided in FIG. 8. The passivation layer 76 includes a window 78that exposes a surface 80 of the conductive layer 70. Further, thepassivation layer 76 and window 78 may be formed through any suitableprocesses, including those discussed above with respect to thepassivation layer 66.

Thus, the redistribution layer formed through step 36 of the method 30generally includes the conductive layer 70 and the passivation layers 66and 76. While the redistribution layer of some embodiments may includeadditional elements or layers, the redistribution layer of otherembodiments consist of, or consist essentially of, the conductive layer70 and the passivation layers 66 and 76. Additionally, it should benoted that, in some embodiments, the redistribution layer is formedwithout relying on any vacuum processes, and is formed entirely throughfabrication processes at pressure, which may reduce the incidence ofdamage to the substrate 42 and/or the carrier 52 from an excessivepressure differential between the sealed cavity of the device 40 and theone or more processing chambers in which the device 40 is disposed forformation of the redistribution layer. For instance, the passivationlayers 66 and 76 may be formed through low pressure and/or atmosphericpressure processes, while the conductive layer 70 may be formed throughone or more APCVD processes or low pressure chemical vapor deposition(LPCVD) processes. In one embodiment, for example, the various layers ofthe redistribution layer are formed in one or more processing chambersin an environment having pressure substantially equal to 1 atm.

Finally, with respect to step 38 of the method 30, various UBM featuresmay be formed on the device 40, as generally illustrated in FIG. 9. Inthe presently illustrated embodiment, a portion of the outer titaniumsub-layer 74 is etched to expose the aluminum layer 72 and the surface80 in preparation for such features. In some embodiments, the titaniumlayer 74 may be etched via wet etch process, which may also serve todescum a surface 80 to facilitate formation of various UBM features.

Particularly, the exposed surface 80 of the conductive layer 70 may beplated with one or more materials, as generally represented by platinglayers 82 and 84, before receiving a contact bump 86. In one embodiment,the plating layer 82 comprises nickel and may be formed through anelectroless deposition process, while the plating layer 84 comprisesgold that is formed through an immersion plating process. In otherembodiments, however, one or both of the plating layers 82 and 84 may beformed through different processes, may be formed of differentmaterials, or may be omitted entirely. Additionally, in one embodiment,the surface 80 undergoes a preparation process, such as zincating, tofacilitate adhesion of the plating layer 82 to the surface 80.

Following any desired plating, a contact bump 86 may be coupled to thesurface 80, either directly or via the one or more plating layers. Thecontact bump 86 may be formed of any suitable, electrically-conductivematerial, such as solder. Notably, the contact bump 86 facilitatesdirect coupling of the device 40 to other circuitry. In someembodiments, the provision of contact bumps 86 may allow for the directcoupling of the substrate 42 to a circuit board without requiringadditional, intervening substrates or wire bonding. For instance, in oneembodiment, contact bump 86 may enable the device 40 to be directlyreceived in a socket of a circuit board, allowing electricalcommunication between features of the substrate 42, such as an imagesensor or imager 28, and various circuitry external to the device 40.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. A method comprising: providing a substrate having a via formedtherein, forming a sealed array, wherein forming the sealed arraycomprises attaching a carrier to a first surface of the substrate suchthat a sealed cavity is formed between the substrate and the carrier;and forming a redistribution layer on the sealed array over a secondsurface of the substrate.
 2. The method of claim 1, wherein thesubstrate comprises a semiconductor wafer.
 3. The method of claim 1,wherein the substrate comprises an image sensor.
 4. The method of claim3, wherein the substrate comprises a layer of microlenses.
 5. The methodof claim 3, wherein forming the sealed array comprises attaching thecarrier to the first surface of the substrate such that the image sensoris disposed within the sealed cavity.
 6. The method of claim 1, whereinforming the redistribution layer comprises: forming a passivation layeron the second surface of the substrate; forming a metal layer on thepassivation layer and in electrical communication with the via; andforming an additional passivation layer on the metal layer.
 7. Themethod of claim 6, wherein the metal layer comprises multiplesub-layers.
 8. The method of claim 7, wherein the metal layer comprisesa first sub-layer including titanium disposed on the passivation layer,a second sub-layer including aluminum disposed on the first sub-layer,and a third sub-layer including titanium disposed on the secondsub-layer.
 9. The method of claim 6, wherein forming the redistributionlayer comprises deposition and patterning of the passivation layer, themetal layer, and/or the additional passivation layer.
 10. The method ofclaim 6, wherein the metal layer is formed through an atmosphericpressure chemical vapor deposition process.
 11. The method of claim 1,comprising forming under-bump-metallurgy (UBM) features on theredistribution layer.
 12. The method of claim 11, wherein forming UBMfeatures comprises plating an exposed metallic surface of theredistribution layer and/or forming a metallic bump on the exposedmetallic surface.
 13. The method of claim 1, wherein the forming of thesealed array and the forming of the redistribution layer are performedin one or more reactor chambers at pressures greater than 0.5 atm. 14.The method of claim 13, wherein the sealed array is formed at a lowerpressure than the redistribution layer, such that the pressure withinthe sealed cavity is less than that of a reactor chamber in which thesealed array is disposed during formation of the redistribution layer.15. The method of claim 1, wherein the redistribution layer is formedwithout a vacuum process.
 16. The method of claim 15, wherein theredistribution layer comprises a plurality of layers formed in one ormore processing chambers at a pressure substantially equal to 1 atm. 17.The method of claim 1, wherein attaching the carrier to the firstsurface is performed at a pressure greater than or substantially equalto 0.5 atm and less than or substantially equal to 0.9 atm.
 18. Themethod of claim 1, wherein the second surface is opposite the firstsurface.
 19. The method of claim 1, wherein attaching the carrier to thefirst surface comprises coupling the carrier to the first surface via anadhesive.
 20. A device comprising: a substrate having an image sensorformed on a first surface of the substrate opposite a second surface ofthe substrate; and a carrier adhered to the first surface of thesubstrate such that a sealed cavity is formed between the carrier andthe first surface.
 21. The device of claim 20, comprising a layer ofmicrolenses disposed over the image sensor within the sealed cavity. 22.The device of claim 20, wherein the carrier comprises glass.
 23. Thedevice of claim 20, wherein the pressure within the sealed cavity isless than 1 atm at 40° C.
 24. The device of claim 20, wherein thesubstrate comprises a via configured to facilitate electricalcommunication between the first and second surfaces through thesubstrate.
 25. The device of claim 20, comprising a redistribution layerformed on the second surface of the substrate.
 26. A system comprising:a processor; a memory device operatively coupled to the processor; andan imager operatively coupled to the processor, the imager comprising: asubstrate including an image sensor; and a carrier adhered to thesubstrate over the image sensor such that a sealed cavity is formedbetween the carrier and the substrate proximate the image sensor. 27.The system of claim 26, comprising a layer of microlenses disposed overthe substrate within the sealed cavity.
 28. The system of claim 26,wherein the substrate comprises the processor.
 29. The system of claim26, wherein the system comprises a digital camera.
 30. The system ofclaim 26, wherein the system comprises a cellular phone.